Production of leather



, Patented July 11,1939

David M.

McQueen, Wilmington. DeL, assignor toll. du Pont deflemourl a Company, Wilmingtml. Del a Delaware No Drawing.

Am Serial No. 290,011

April}, ms.

4 Mains. (Gl- 148-5) This invention relates to the tanning of hides, and is more particularly directed to compositions and processes for tanning wherein there is employed a sulfamate of chromium, aluminum, or

5 titanium. p

Chromium, aluminum,- and titanium have customarily been used for the tanning oi hides. in the form of sulfates or basic sulfates.

Now, I have found that hides may eflectively i0 and advantageously be tanned using sulfamates of chromium, aluminum, or titanium.

According to the processes ofmy invention, hides are subjected to the action of a solution of a sulfamate of chromium, aluminum, or titanium l5 and tanning is then eflected by raising the pH of the tanning solution by the addition of a suitable alkali such assodium bicarbonate.

, The processes of my invention may be better understood by reference to the following illustrative examples.-

Example I A solution containing ten per cent of chromium suliamate by weight was prepared. Pickled calf skins were added to the tanning solution and the 26 pH was raised by the successive addition of portions of sodium bicarbonate. The bicarbonate addition was carried to a point such that sixty parts of suliamate radical, NHrSOs, were combined with one gram atomic weight of the chro-' mium present: that is to say, fifty-two parts by weight of chromium. A soft, pleasing leather was obtained aiterflve hours of tanning.

Hides were similarly tanned with a chromium sulfamate tanning solution having a basicity of ninety-six; that is to say ninety-six parts of the suliamate radical tor fifty-two parts of chromium, Good leather was produced by this alternative procedure, but' the time required for tanning was somewhat greater.

" Example II Pickled calf skins were drummed for fifteen minutes in a sodium chloride solution. The solution was made up with flity parts by weight of water and three parts by weight of sodium chloride for each hundred parts by weight ofcalf skins. I At the end of fifteen minutes drumming there was added for each hundred parts by weight of calf skins 21.4 parts by weight of aluminum sulfamate in fifty parts by weight of water. The sulfamate solution also contained 2.55 parts by weight of sodium carbonate for each hundred parts by weight of calf skins.

Alter the addition of aluminum sulfamate the skins were drummed two and a half hours, and. then-there was added 2.55 parts by weight of sodium carbonate for each hundred parts by weight of pickled calf skins. After another hour of drumming 1.28 parts by weight of sodium car- 5 bonate per hundred parts by weight of'calf skins was added, and after still another hour of drumming 1.28 parts by weight of sodium carbonate per hundred parts by weight of calf skins was added. After another hour of drumming the tanhing was complete. A white leather of good character was obtained.

It will be understood that the sulfamate's shown in the examples are only illustrative and that any other sulfainate of chromium, aluminum, and titanium may be used according to my invention. Tltanyl sulfamate (TiO(S.OaNH2)2), for instance, could be used for the tanning of hides with a process similar to those shown above.

The chromium sulfamates used may range in composition from normal chromium sulfamate, Cr(SO=N'Hz)a, to sulfamates containing successively smaller amounts of sulfamate radical and successively correspondingly larger amounts of hydroxyl radical as produced by the addition of a suitable alkali.

The considerations as to the basicityand pHof the tanning solutions are substantially those known to the art in connection with the use of sulfates and basic sulfates of chromium. alu- 3O minum, and titanium, and the pH may readily be adjusted by the use of a suitable alkali. such as sodium bicarbonate in accordance with known practices.

The technique oftanning and the manipulative steps involved do not differ substantially from the practices known for tanning processes using other compounds of chromium, aluminum, and

titanium and those skilled in the art will readily be able to adapt such practicesto processes ac- 40 cording to my invention.

It will be observed that the term "hide has been used herein in its generic sense as covering skins of all varieties as well as the heavier and larger skins sometimes specifically designated as hides.

While I have shown certain specific compositions and processes herein, it will be understood that without departing from the spirit of my invention those skilled in the art may readily devise numerous compositions and processes em ploying suliamates of chromium, aluminum, or titanium for-the tanning of hides.

I claim:

1. In a process for tanning hides, the step comprising subjecting a hide to a tanningvsolution containing a sulfamate of a metal selected from the group consisting of chromium, aluminum, and titanium.

2. In a. process for tanning hides, the step comprising subjecting a, hide to a tanning solution containing a chromium sulfamate.

3.- In a process for tanning hides, the step comprising subjecting a. hide to a. tanning solution containing an aluminum sulfamate.

4. A tanning composition comprising a sulfamate of a. metal selected from the group con- 5 sisting of chromium, aluminum, and titanium.

- DAVID M. MCQUEEN. 

